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Mussels (Mytilus spp.) are one of the most cultivated and commercialized bivalves in southern Chile; culture is currently supplied almost entirely from wild-caught seed obtained from relatively few collection centers. The genetic diversity and differentiation of the blue mussel in southern Chile was investigated by sampling six locations: one natural bank and five seed collection centers. Nine polymorphic microsatellite (SSR) loci were genotyped (Mgu1, Mgu3, MT203, MT282, Mg15, Mg56, Med737, MIT02 and MGE005). We found 75 different alleles, six of which were private alleles. Of the analyzed loci, 45 of 54 tests performed deviated from Hardy-Weinberg equilibrium after sequential Bonferroni correction (P < 0.05), revealing significant heterozygote deficiencies. The polymorphic information content (PIC) ranged from 0.322 (MGE005) to 0.893 (Mgu1). Despite the long distance between some sampling sites (up to 1360 km), genetic differentiation among the sites was low (F ST = 0.043, P < 0.0001). The Bayesian cluster analysis (STRUCTURE) indicated two probable clusters, while the non-parametric cluster analysis (AWclust) identified two to four clusters. Both analyses showed a high level of admixture within clusters. Our results indicate that blue mussels in southern Chile show lower genetic diversity than in other countries, low inbreeding levels, and limited genetic differentiation among locations.

Mussels are one of the most cultivated and commercialized bivalves worldwide and in southern Chile its culture represent an important economic activity. The species identification within the Mytilus genera, by morphological features, is unreliable, so we used a polymorphism RFLP in the gene encoding the polyphenolic adhesive protein as a species-specific genetic marker to describe Mytilus species diversity in southern Chile, and evaluate possible applications in traceability, food quality and safety. Using Me 15-16 marker most mussels were M. chilensis, finding no other pure individuals; however, putative hybrids of M. chilensis x M. trossulus and M. chilensis x M. galloprovincialis were detected. There was no evidence of M. edulis. The presence of the M. trossulus allele, faraway from its distribution area, demands further analysis with different genetic markers to allow a better understanding of its origin. In addition, the correspondence between markers that distinguishes northern from southern hemisphere M. galloprovincialis, with those who discriminates between M. chilensis and M. galloprovincialis would contribute to the taxonomic status of Chilean blue mussels. In Chile, the genetic composition of Mytilus indicates that geographical origin of mussels and its traceability cannot be established merely from the identification of the species. The use of other markers would be required.Los mejillones son una de las especies de bivalvos más cultivadas y comercializadas, en el sur de Chile donde su cultivo representa una actividad económica importante. La identificación de la especie dentro del género Mytilus, basada en las características morfológicas no es confiable por lo que se utilizó un polimorfismo RFLP en el gen que codifica la proteína adhesiva polifenólica como marcador genético específico de la especie para describir la diversidad de especies Mytilus en el sur de Chile, y evaluar posibles aplicaciones en trazabilidad, calidad e inocuidad de los alimentos. Usando el marcador Me 15-16, la mayoría de los mejillones fueron M. chilensis, no se encontraron individuos puros de otras especies. Sin embargo, se detectaron híbridos putativos M. chilensis x M. trossulus y M. chilensis x M. galloprovincialis. No se encontró evidencia de M. edulis. La presencia del alelo de M. trossulus, lejos de su área de distribución, requiere de análisis posteriores con diferentes marcadores genéticos para entender su origen. Además, conocer la correspondencia entre marcadores que distinguen M. galloprovincialis del hemisferio norte y sur con aquellos que discriminan entre M. chilensis y M. galloprovincialis contribuirá al estatus taxonómico del mítilido chileno. La composición genética de Mytilus en Chile no permite establecer su origen geográfico ni la trazabilidad, basándose solo en la identificación de la especie y se requiere el uso de otros marcadores.

In trout farming males exhibits lower growth rate and precocious sexual maturation in contrast to females. Since these traits are detrimental for intensive production, all females populations are most appreciated by fish farmers. Molecular markers sex-specific have been developed for rainbow trout that can be useful to diagnose the phenotypic sex of individuals. We evaluated the use of two SCAR markers (OmyP9 & Omy163), which show polymorphisms between males and females in rainbow trout as a diagnostic test for sexing farmed trout. Adult trout (n = 131) were genotyped to assess the association of the SCAR markers with phenotypic sex. To evaluate the correct performance of the SCAR marker in sex diagnosis, each marker and both were analyzed to estimate its specificity (the proportion of males that are correctly identified), sensitivity (the proportion of females that are correctly identified) and predictive value (the probability of the correct positive or negative female identification). Significant associations with phenotypic sex of both SCAR markers with sex were found. The sensitivity and predictive (positive and negative) indexes show higher values when both SCAR markers were considered (95.7, 77.4 and 94.4%, respectively). For joined SCAR markers a likelihood ratio (LR+) of 3.43 was obtained indicating its utility to establish a diagnostic test for sexing trout by use of marker-based analysis.En el cultivo de truchas los individuos del sexo masculino presentan menor tasa de crecimiento y maduración sexual precoz, características que no presentan las hembras. Debido a estos rasgos indeseables para el cultivo intensivo, el uso de poblaciones todo hembra es una práctica habitual en el cultivo de truchas. Para trucha arcoíris se han desarrollado marcadores moleculares sexo específico que pueden utilizarse en el diagnóstico temprano del sexo, en condiciones de cultivo. Se evaluó la aplicación de dos marcadores SCAR (OmyP9 y Omy163), que muestran polimorfismos entre los sexos en esta especie. Con ambos marcadores se genotipificaron 131 truchas para evaluar su asociación con el sexo fenotípico. Para determinar la utilidad en diagnóstico del sexo de cada marcador SCAR por separado, y en conjunto, se determinó la especificidad, sensibilidad y valores predictivos en la detección de un individuo de sexo femenino. Se comprobó la asociación significativa descrita para ambos SCAR con el sexo fenotípico. La mayor sensibilidad y valores predictivos positivo y negativo se obtuvo usando ambos marcadores simultáneamente (95,7; 77,4 y 94,4%; respectivamente). El valor de razón de verosimilitud (LR+ =3,43) mostró que la mejor prueba de diagnóstico para detectar hembras es usar conjuntamente OmyP9 y Omy163.